The Collaborative International Dictionary of English v.0.48:

Shaky \Shak"y\, a. [Compar. Shakier; superl. Shakiest.]
   1. Shaking or trembling; as, a shaky spot in a marsh; a shaky
      hand. --Thackeray.
      [1913 Webster]

   2. Full of shakes or cracks; cracked; as, shaky timber.
      --Gwilt.
      [1913 Webster]

   3. Easily shaken; tottering; unsound; as, a shaky
      constitution; shaky business credit. [Colloq.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

shaky
    adj 1: inclined to shake as from weakness or defect; "a rickety
           table"; "a wobbly chair with shaky legs"; "the ladder
           felt a little wobbly"; "the bridge still stands though
           one of the arches is wonky" [syn: rickety, shaky,
           wobbly, wonky]
    2: vibrating slightly and irregularly; as e.g. with fear or cold
       or like the leaves of an aspen in a breeze; "a quaking bog";
       "the quaking child asked for more"; "quivering leaves of a
       poplar tree"; "with shaking knees"; "seemed shaky on her
       feet"; "sparkling light from the shivering crystals of the
       chandelier"; "trembling hands" [syn: shaky, shivering,
       trembling]
    3: not secure; beset with difficulties; "a shaky marriage" [syn:
       precarious, shaky]

Moby Thesaurus II by Grady Ward, 1.0:

208 Moby Thesaurus words for "shaky":
   adrift, afloat, agitated, aguey, aguish, algid, all shook up,
   all-overish, anile, aquiver, aspen, bagging, baggy, bashful,
   blue with cold, blurred, breathy, chattering, chilly, choked,
   choking, clear, cold, cool, cowardly, crabbed, croaking, dangerous,
   dangling, debilitated, decrepit, desultory, dickey, diffident,
   dilapidated, dithery, doddered, doddering, doddery, doubtful,
   drawling, drawly, drooping, dubious, dysphonic, easy, fearful,
   fearing, fearsome, feeble, fidgeting, fidgety, flapping, flimsy,
   floating, fluctuant, fluttery, fossilized, free, frozen,
   frozen to death, gerontal, gerontic, goosy, groggy, guttural,
   half-frozen, hanging, harsh, hawking, hazardous, hoarse, iffy,
   in a quiver, in fear, inarticulate, indecisive, indistinct, infirm,
   insecure, insubstantial, jittery, jumpy, lax, lisping, loose,
   mispronounced, mossbacked, moth-eaten, mousy, mummylike, muzzy,
   nasal, nervous, palsied, papery-skinned, perilous, precarious,
   problematic, provisional, quaking, quavering, quavery,
   questionable, quivering, quivery, rabbity, rachitic, rackety,
   ramshackle, rattletrap, ravaged with age, relaxed, ricketish,
   rickety, risky, rocky, rootless, run to seed, rusty, scary, senile,
   shaking, shifting, shifty, shivering, shivery, shook up, shrinking,
   shriveled, shuddering, shy, skittery, skittish, slack, slippery,
   sloppy, snuffling, spidery, spindly, startlish, stifled, strangled,
   streaming, stricken in years, succussatory, succussive, suspect,
   teetering, teetery, temporary, tentative, tenuous, thick, throaty,
   ticklish, timeworn, timid, timorous, tottering, tottery,
   treacherous, trembling, trembly, tremulant, tremulous, trepidant,
   trigger-happy, tumbledown, twangy, twitchy, twittery, unanchored,
   unbound, uncertain, unclear, undependable, undone, unfaithworthy,
   unfastened, unfixed, unhealthy, unpredictable, unreliable, unsafe,
   unsettled, unsolid, unsound, unstable, unsteadfast, unsteady,
   unstuck, unsubstantial, unsubstantiated, unsupported, unsure,
   untied, untrustworthy, vacillating, velar, vibrating, wavering,
   weak, with chattering teeth, withered, wizened, wobbling, wobbly